Reconstituted tobacco

ABSTRACT

A method of making reconstituted tobacco material from stem material is disclosed which involves mechanically working by crushing or flattening stem particles, before it is subjected to any soaking or wetting operation, in such wise that the cellular structure of the stem material is disrupted without significant reduction in the size of the particles. The thus treated material is then refined, mixed with an aqueous carrier to form a slurry, shaped and then dried to a predetermined moisture level. Subsequent to the mechanical working operation, the stem material may be sweated to expand the cellular structure.

iltiited States Patent Blewitt et al.

[ 5] Mar. 7, 1972 [54] RECONSTITUTED TOBACCO [72] Inventors: Donald Joseph Blewitt, Richmond, Va.;

[52] 115.01. ..131/140c,131 17,131/140R 51 Int. Cl. q ..A24b 03/14 [58] FieldofSearch ..131/140,17,140R,141,142, 131/143, 144

[56] Reierences Cited UNITED STATES PATENTS 2,433,877 1/1948 Wells et al. ..131/17 A 3,513,857 5/1970 Silberman..... ....131/140 3,464,422 9/1969 Light ....131/140 267,764 11/1882 w66d..... ....131/140 R 1,068,403 7/1913 Maier..... ....131/140 R 3,125,098 3/1964 Osborne ..131/140 R 3,409,028 11/1968 de la Burde Bl/140R 3,435,829 4/1969 Hind et al...

1,202,302 10/1916 Moonelis ..::..131/1s c FOREIGN PATENTS 0R APPLICATIONS 25,830 4/1903 Great Britain ..131/140 R Primary Examiner-Melvin D. Rein Attorney-George W. Price and Murray Schaffer [57] ABSTRACT A method of making reconstituted tobacco material from stem material is disclosed which involves mechanically working by crushing or flattening stern particles, before it is subjected to any soaking or wetting operation, in such wise that the cellular structure of the stem material is disrupted without significant reduction in the size of the particles. The thus treated material is then refined, mixed with an aqueous carrier to form a slurry, shaped and then dried to a predetermined moisture level. Subsequent to the mechanical working operation, the stem material may be sweated to expand the cellular structure.

18 Claims, No Drawings 1 nEcoNs'rrrurEo TOBACCO The present invention relates to the manufacture of reconstituted tobacco compositions of the type that can be manufactured without nontobacco additives. More particularly, this invention relates to processing improvements in the manufacture of reconstituted tobacco products containing substantial amounts of refined tobacco stems, said processing improvements providing a degree of control of product properties previously attainable only through the use of nontobacco additives.

Processes for the formation of reconstituted tobacco compositions are well known in the art. Some of these processes have been eminently successful, others not so. Processes for the manufacture of reconstituted tobacco compositions may be classified as to whether nontobacco additives are or are not employed as product constituents. Prior to the present invention, all of the reconstituted tobacco processes which have achieved substantial commercial success have relied on the use of nontobacco additives to provide the required product properties. The reliance upon nontobacco additives to provide specific product properties is easy to understand. For example, if the reconstituted tobacco product burns with an undesirable black ash, the easiest solution involves the addition of a small amount of inorganic whitener. If the reconstituted tobacco product is too brittle, add humectant; if it molds too rapidly, add fungicide; if it is the wrong color, add whiteners, darkening agents or food-approved colorants. For the vital property of sheet strength and coherence, it is far easier (and often less expensive) to grind all the tobacco into dust form and use nontobacco gums or adhesives as binding agents rather than to develop processes which utilize adhesives and fibers in the tobacco plant itself. In general, for every functional property desired in the reconstituted tobacco product, a nontobacco ingredient can be found which will contribute this property.

However, tobacco products containing nontobacco additives frequently suffer in taste and burn aroma characteristics by dint of their nontobacco portions. Although nontobacco additives vary greatly in the extent to which they adversely affect these taste characteristics, they invariably contribute either nontobacco tastes or aromas on combustion or little taste and aroma on combustion. In the former situation, the presence of the nontobacco combustion characteristic contributes off-notes to the product, while in the latter case the absence of a tobaccolike combustion characteristic detracts from the product quality.

Additionally, from a purely economic and commercial viewpoint, it is advantageous to make reconstituted products solely out of all natural tobacco components and to fully use those portions of the tobacco leaf such as its production stems, veins and pulp which are presently not usable. Furthermore, in some countries it is contrary to law to produce reconstituted tobacco compositions containing nontobacco additives. In such countries, only 100 percent tobacco reconstituted compositions are permitted, and all required product properties must be developed during the tobacco processing operation itself.

In pending U.S. Pat. application Ser. No. 661,762 by H. J. Light and R. J. Osborne, now US. Pat. No. 3,464,422 is described a process in the making of 100 percent tobacco reconstituted compositions by refining tobacco stems and/or stalks until at least the point where the Schopper-Riegler freeness value reaches a minimum value and then increases with further refining; that is, to an inverted Schopper-Riegler freeness value. The process described in that application contributes immeasurably to the production of 100 percent tobacco reconstituted products with strength and unifonnity characteristics far superior to all alternate procedures proposed previously.

This invention relates to novel processing innovations which eliminate undesirable product characteristics without the use of nontobacco additives, as well as improve the overall process economics and reproducibility. These processing innovations have resulted in the first percent tobacco reconstituted products which satisfy the stringent requirementsfor commercial acceptability. These requirements include tensile strength, color, ability to shape or form, and the numerous smoking qualities such as taste, aroma, burn and ash characteristics.

Accordingly, the present invention provides a method for producing reconstituted tobacco compositions in economical and commercially acceptable form without the need for usage of nontobacco additives. This method comprises a series of processing steps, each with significance to the overall process economics or reproducibility or to specific product properties, which extend from the preparation of the tobacco to the ultimate formation of a smoking product. These novel processing steps and the novel combination of these steps result in an overall process which can transform normally unusable tobacco material into 100 percent tobacco reconstituted products of considerable commercial value.

It is accordingly among the objects of this invention to provide a method for manufacturing tobacco compositions of commercially desirable quality and economics without the need for nontobacco additives.

It is a further objective of this invention to provide a method for manufacturing 100 percent tobacco compositions wherein the product strength, color, taste and ash characteristics can be controlled and modified to commercially acceptable ranges without resorting to the use of nontobacco additives.

A further object of the present invention lies in the provision of novel, specific methods for preparing tobacco stem or stalk material for effective utilization in the manufacture of reconstituted tobacco compositions.

These and other objects and advantages are contained and will be fully apparent from the following account of the invention. It should be noted prior to this discussion that the term tobacco stems shall include tobacco stems, tobacco stalks, or mixtures thereof.

In order to facilitate this discussion, the novel processing will be considered individually at first, with discussion of the interrelationships in the overall process being reserved until afterwards.

1. WORKING OF STEMS In the preparation of tobacco stems for sheet formation, prior processes generally involved addition of limited quantities of dried stems to water, followed by subjection of the wetted mass to chemical and/or physical treatment to transform the stem material into a form suitable for incorporation with major portions of lamina and leaf, into sheet or other shape formation. In the practice of such processes, it is found that the nonuniformity of the initial tobacco stems, which vary in size, density, and to some extent chemical composition, results in considerable variations in the time and energy requirement for comminution to a fonn suitable for the shaping of reconstituted products. Such variations are particularly obvious in processes, such as the one described in the Light and Osborne application, which do not involve chemical treatment prior to the subjection of the stem-water mixture to mechanical work energy to open up the stem structure. In such processes, variations in particle size, density and composition greatly affect the penetration of water and the rate of disintegration under the influence of even the most reproducible forms of mechanical energy input, and have limited the amount of stems utilized for such purposes.

As a result, the amount of energy and time required to refine tobacco stems to a particular inverted Schopper-Riegler freeness value by the method of Light and Osborne may vary considerably and is unpredictable from batch to batch. It is obvious that such a situation is undesirable from a process and manufacturing standpoint.

In the present invention, it has been found that if the stems having a moisture content of about 30 percent are mechanically worked as by crushing or flattening under pressure prior to dispersion in water and mechanical refining, the rate of the subsequent mechanical refining becomes predictable and reproducible from batch to batch. This would indicate that the working operation tends to even out structural variations between the stems so that a reproducible form of energy input will result in a reproducible rate of disintegration of the stems. As noted, the working of the stems includes procedures of flattening and crushing. Working is intended to define the mechanical handling of stem so as to deform its structure without cutting or otherwise destroying the integrity of the stem particle.

An additional and novel benefit which has been found to result from the working of stems prior to refining to a pulpy mass is that the time required to refine to a particular freeness value is significantly reduced, thus making the overall process even more attractive economically. In most cases, the working of the stems prior to refining reduces the refining time by about 50 percent, and in some cases reductions of as high as 75 percent in time have been recorded. It is intimated from such results that the working process must disrupt the cellular structure of the stems to the point that they are more easily disintegrated under the action of the mechanical work. Accordingly, it is a teaching of this invention that the working of stems prior to refining results in more regular and reproducible refining rates, as well as decidedly shorter refining time requirements. Such a stem working operation has been found to have no significant adverse effects, since the strength properties of reconstituted sheet made from such stems is similar to that from stems without this pretreatment.

2. SWEATING OF STEMS The sweating of whole tobacco is normally employed to improve its flavor and smoking quality. The process as normally employed tends to reduce the content or effect of harsh ingredients, decrease enzyme activity and equalize the flavor characteristics of a variable starting material. Such sweated tobacco is directly employed in the manufacture of cigarettes or cigars. As opposed to the relatively mild forms of sweating employed in connection with the use of whole leaf to affect taste characteristics, it has been found in the present invention that a hard force-sweat of tobacco stems alone prior to the refining operation has several novel and unforseeable results. The refined stems which have been hard force-sweated are found to result in reconstituted tobacco products which are significantly stronger than those prepared from the same stems without the hard force-sweating operation. Additionally, although excessive sweating in bulk of whole leaf is well known to have detrimental effects on tobacco taste properties, the hard force-sweated stems of this invention when converted into reconstituted tobacco products are found to have substantially improved taste and smoking qualities as compared to the same products prepared without the hard force-sweat pretreatment.

The term sweating" as used herein is to define that exothernic process wherein fennentation of tobacco causes a temperature buildup and subsequent indigenous and in situ moistening or perspiring of the tobacco. In Bulk sweating, tobacco is piled unrestrained in open storage and at ambient temperatures and pressures for a period of at least one week. Case sweating, on the other hand, merely defines a similar process, except that the tobacco instead of being freely piled is contained in boxes or cases open to ambient temperature and pressure conditions.

The sweating of stems in bulk is preferably, according to this invention, carried out after they have been flattened or crushed, since in this form it is easier to attain the hard forcesweat condition. Unflattened stems do not, because of their low-bulk density, lend themselves to efficient high-temperature force-sweats. The worked stems are sweated in bulk in ambient temperatures in the range of l30-l50 F. It is extremely fortunate that the stem-working operation, which was described previously as having a desirable influence on the uniformity and time of refining, should also be a help in the ef-. fective hard force-sweating of the stems with its advantages in product strength and smoking quality.

The sequence of operations involved in the overall integrated process will be described later in this specification.

3. PREWASHING OF STEMS Among the problems frequently encountered in the manufacture of 100 percent tobacco reconstituted products are insufficient strength, unsatisfactory taste and smoking quality, a color which is too dark, an ash which is too dark in color or not of sufficient coherence, or a product which on refrigerated storage will develop unsightly crystals of potassium nitrate on the surface. The problems are aggravated and increase in proportion to the amount of stem particles employed.

Surprisingly, all of these problems can be eliminated or reduced to commercially acceptable levels by prewashing of the worked stems with water. By washing the stems prior to refining of the stems, there is removed tobacco solubles which cause these problems to occur.

In a preferred embodiment of this procedure, the flattened or crushed stems are placed in a tank containing 10 parts of water to 1 part of flattened stem. The mixture is agitated and allowed to soak for at least a half hour depending on the nature and size of the stem. During this soaking period the stem material rises to the surface and a tobacco liquor containing the tobacco solubles may be drawn off from the bottom of the tank. All of the tobacco liquor or any desired fraction of the tobacco liquor, as dictated by the product properties desired, may be removed and replaced with clear fresh water. The stem-water mixture is then refined or otherwise macerated in the normal manner.

The effects of removal of stem solubles prior to refining are many fold. The greater the proportion of stem solubles removed, the lighter the color of the resulting reconstituted tobacco product. The greater the proportion of stem solubles removed, the greater the strength of the ultimate reconstituted tobacco product, since the refined stem insolubles rather than the solubles are the source of the ultimate product strength.

On the other hand, the stem solubles in the tobacco liquor contain a number of constituents, some whose origin was the soil and/or plant nutrients, which are known to cause or contribute to poor tobacco burn characteristics. Among these undesirable soluble constituents are chloride and phosphate ions which inhibit the burn, as is manifested in reductions in the free burn rate and burn duration of the ultimate reconstituted tobacco product, as well as in an undesirable dark-colored ash due to incomplete combustion. Magnesium ions, which are also present in the stem solubles portion, have been found to cause flowering" of the ash and to adversely affect the ash coherency. These and other substances in the tobacco liquor have inhibiting influences on the tobacco burn characteristics and adverse affects on the tobacco ash characteristics, and to the extent that the soluble portion of the stems is removed, these burn and ash characteristics are improved. In practice, the minimum quantity of tobacco solubles should be removed consistent with attainment of satisfactory properties, since the removal of a portion of the tobacco affects the process economics.

The taste and smoking quality of the reconstituted tobacco product are improved through removal of stem solubles in several ways. First, it is well known that the burn and the taste properties of smoking articles are related, and that improvement of the burn property is generally accompanied by a taste and smoking quality improvement. As a result, removal of soluble bum-inhibiting salts as described previously results in definite taste improvements. Second, since removal of all or a portion of the stem solubles results in significant strength increases, one is able to load" the reconstituted tobacco product with a higher percentage of ground leaf dust and still produce a product with a strength characteristic consistent with the requirements of the end-use application. Since leaf dust is generally superior to stem solubles in smoking quality, the substitution of additional quantities of the former for the latter in the reconstituted tobacco formulation upgrades the smoking quality of the product. As an example of the principle involved here, a formulation comprised of 80 percent refined unwashed stems and 20 percent leaf dust may have acceptable strength properties. However, if the stems are fully washed before refining, a formulation of similar strength may be prepared from only 40 percent refined washed stems and 60 percent leaf dust, with decidedly improved smoking quality.

Additionally, some tobacco stem types, especially Burley stems, contain appreciable quantities of nitrates. Since potassium nitrate has limited solubility in water, cold storage of moist reconstituted tobacco products made from high-nitrate tobaccos frequently results in the growth of large unsighly potassim nitrate crystals on the surface of the product. Prewashing of the stems and removal of at least a portion of the stem solubles is generally sufficient to eliminate this problem.

In cases where possible trace contamination of the reconstituted tobacco product with a nontobacco additive is considered permissible, the flattened stems may be washed with a dilute solution of a mineral acid such as nitric acid or of an organic acid such as acetic acid. In this process, the proper quantity of acid in the range of 0.1 to percent based on the total liquid is dissolved in the water, and the flattened stems are introduced and soaked with occasional stirring for 30 to 180 minutes. The supernatent liquid is drained off and the stems are rinsed with clean water and allowed to drain. After the required amount of fresh water has been added for attainment of the desired pulp consistency, the stems are ready to be refined to the predetermined degree.

4. ELIMINATION OF TOBACCO DUST GRINDING As was mentioned in several instances above, in the usual preparation of 100 percent tobacco reconstituted products, the usual practice is to combine refined tobacco stems with ground tobacco dust to provide a formulation with the optimum strength, smoking quality and economics for the intended application. The ground tobacco dust is prepared by dry grinding in hammer mills or other grinding devices to the required particle size.

It has been found in the present invention that the expense of equipment and labor involved in dry grinding of tobacco dust can be eliminated by incorporation of the leaf portions without grinding directly into the stem pulp at the point that the refining has proceeded to approximately the inversion point on the Schopper-Riegler scale and before the pulp has passed to the negative portion of the scale. Subsequent refining of the stems and leaf disintegrates the leaf portions to the extent that the product is indistinguishable from one to which the corresponding amount of dry ground leaf dust is added in the conventional manner.

SEQUENCE OF PROCESSING STEPS T he processing improvements described above may be severally or jointly incorporated into the manufacturing sequences of conventional processes for the manufacture of 100 percent tobacco reconstituted products to provide improved tobacco products.

The sequence of operations in the overall process may be as follows:

a. Flatten or roll tobacco stems to improve uniformity of b. The flattened or rolled stems are then subjected to a hard force-sweat to improve the ultimate product strength and smoking quality properties.

. The flattened and sweated stems are then thrashed so that d. The flattened stems retained on the 4-mesh screen are suspended in approximately 10 times their weight of water and, after a suitable soaking period for extraction of solubles, all or a suitable portion of the tobacco liquor is drained from the tank. The amount of solubles removed (i.e., the portion of liquor drained) depends on the degree to which it is desired to raise tensile strength, lighten color, improve burn properties and ash color and coherence, improve smoking quality and remove crystallizable nitrates. Tobacco liquors removed in the washing process may be replaced with water so that viscosity is maintained.

The stem-water mixture is now refined by milling or grinding, suitable techniques being described for example in US. application Ser. No. 661,762 by Light and Osborne.

f. Although it is not absolutely necessary to add dry ground tobacco dust or the undersized stem (which is also otherwise waste material) to the refined stem pulp, this is usually done for reasons of taste and smoking quality, burn and process economics. Dry ground tobacco dust which generally weakens the ultimate product may be added in amounts which usually range from 20 to 70 percent of the final product, depending on the strength characteristics of the refined stem pulp, the degree to which the stems were washed and the requirements for strength, burn and smoking quality in the reconstituted tobacco product. As an alternative, the undersized portions of the thrashed flattened stems, dust and other tobacco leaf fragments may be added to the stem pulp during the course of its refining. This alternative eliminates the need for dry grinding. During this step of addition of dry tobacco proper moisture and viscosity levels are maintained to provide a consistency suitable for shaping.

. It has been found desirable to prevent the temperature of The resultant aqueous mixture of refined tobacco stems and tobacco dust may be deaerated by the application of suitable vacuum with the proper amount of agitation to facilitate removal of air. Deaeration results in stronger products with a uniform appearance. It may be omitted when the strength of the undeaerated product is sufiicient for the application and when the appearance of airholes in the product is not objectionable or when the aqueous mixture is devoid of excess gas.

An optional stem involves homogenization of the tobacco slurry composition prior to shaping, to provide a more uniform and mottle-free structure during the shaping process. Homogenizing may be accomplished by use of conventional techniques.

. The last step is the casting, molding or shaping and sub- EXAMPLE 1 Chopped Maryland Stems, l-2 inches average length, are put into a commercial Guardite"*(*Reg TM of the American Machine and Foundry Company for apparatus for the moisture treatment of tobacco.) unit and are steam softened for 3 hours using a standard Guardite softening procedure involving successive cycles of vacuum and steam to facilitate penetration of moisture and softening. At the end of this period, the stems are softened and have a moisture content of 35-45 percent. The stems are then crushed or flattened under pressure using a conventional Lanhoff crusher with a clearance of 1-2 mils between the flattening rollers. After flattening, the size of the stems averages about three-fourths inches width, 3 inches length and about l-2 mils thick. The stems are then dried to about 8-15 percent moisture content and transferred to a threshing machine with y-inch concave openings. The number 4 crush fraction is separated; this is the fraction retained on a 4-mesh screen. The size of these crushed stems is approximately one-fourth-three-eighths inches in length and width. The particles that are too fine that are produced in the threshing process are separated and combined with the tobacco dust fraction used in reconstituted tobacco sheet formulations. Alternately, the finer material may be included with the number 4 crush fraction in the subsequent refining operation.

The refining of these stems is started after adding sufficient water to produce a solids content of 7 percent. A singleor a double-disc refiner may be employed to refine the stems. A twotank refining system is employed, in which the stem-water dispersion is pumped back and forth between two tanks, going through the refiner, located between the tanks, each time until the requisite degree of refining is attained. An alternate procedure is to use only one tank, and to continuously cycle from this tank through the refiner and back into the same tank until refining is complete. The use of precrushed stems allows better flow through the system, and the disruption of the cellular structure caused by crushing results in decidedly earlier separation and fibrillation of the stem structure, and with reduced power consumption. This ease of refining further manifests itself in lower stem pulp temperatures generated during the refining process, with beneficial effects on the ultimate product color and taste.

The time required to refine crushed Maryland Stems in this manner to an inverted freeness of minus 400 cc. using the standard Schopper-Riegler freeness test was found to be 100 minutes.

The refined Maryland Stem were combined with Manila Leaf in a 70/30 ratio (Refined Maryland Stems/Manila Leaf) on a solids basis with additional water to produce a solids content of 8 percent for the total dispersion. The dispersion was cast on a moving stainless steel belt, dried by steam impingement on the underside of the belt, remoistened to about 23 percent moisture content and doctored in sheet form from the belt. The properties of this reconstituted sheet, at 23 percent moisture content and at a sheet thickness of 5.0 grams/ft. is shown below. Tensile properties were measured on l-inch width strips on a standard Scott Paper Tester.

For comparison, using the same refining system and refining to the same point with uncrushed Maryland stems required 620 minutes of refining. Reconstituted tobacco sheets prepared from these uncrushed Maryland stems were found to be of comparable sheet strength to that of the crushed stem formulation.

EXAMPLE 2 Pennsylvania tobacco stems are prepared for refining as in Example 1, except that after the Guardite softening and Lanhoff flattening operations, the flattened stems at 35-45 percent moisture content are subjected to a bulk or case sweating operation prior to the threshing operation to obtain the number 4 crush size. In bulk sweating, lots of 10,000 to 20,000 lbs. of flattened stems at 35-45 percent moisture content are piled in a bin at ambient temperature and pressure. As a result of the high-bulk density resulting from the flattening operation and the high-moisture content, a high-temperature force sweat condition is attained and a sweating temperature in the mass of l30150 F. results. The sweating is allowed to continuefor a period of 4 weeks, during which time the pile of stems is turned several times to insure a uniformly sweated product.

After the sweating operation, the sweated stems are dried to about 8-15 percent moisture content and are threshed to the number 4 crush size as in Example 1. The stems were then suspended in water to produce a stem-water mixture at about 6 percent solids, and then refined tovan inverted Schopper- Riegler freeness value of minus 200 cc.

The refined sweated Pennsylvania stems were then combined with Manila leaf dust in the ratio of 70/30 (Refined Sweated Pennsylvania Stems/Manila Leaf) and the dispersion was cast into a sheet as per Example 1.

The properties of this reconstituted sheet formulation measured as in Example I is as follows:

Sheet Strength Type grams/inch 70/30 Sweated Penna Stems] Manila Leaf 510 For comparison, similar formulations were prepared using unsweated Pennsylvania stems prepared and refined exactly as described previously except without the sweating operation. The properties of the counterparts of the formulations above but made with refined unsweated Pennsylvania stems are as follows:

Sheet Strength Type grams/inch 70/30 Unsweated Penna. Stems/ Manila Leaf EXAMPLE 3 The procedure of Example 2 was followed exactly, however, the refined sweated Pennsylvania stems were combined in a 70/30 formulation with Pennsylvania Leaf. The properties of the resultant sheet is as follows:

A comparison sheet of unsweated Pennsylvania Stems and Pennsylvania Leaf prepared in exactly the same way had the following properties:

Sheet Strength Type grams/inch l 0 70/30 unsweated Penna.Stemsl Penna.Leaf 450 EXAMPLE 4 The procedure of Example 2 was followed exactly,.however, the refined sweated Pennsylvania stems were combined in a 70/30 formulation with Havana Seed Leaf. The properties of the resultant sheet is as follows:

Sheet Strength Type grams/inch 70/30 Sweated Penna.Stems/ Havana Seed Leaf 625 A comparison sheet of Unsweated Pennsylvania Stems and Havana Seed Leaf prepared in exactly the same way had the following properties:

EXAMPLE 5 The procedure of Example 2 was followed exactly except that as an alternate to bulk sweating the Pennsylvania Stems were case sweated. In the alternate sweating procedure, case sweating, the flattened stems at 35-45 percent moisture content are loaded into cases, using about 350 lbs. to a case. The cases are stored in a room with a room temperature of about 90l 10 F. for 4 weeks. During this period, a sweating temperatui e inside the cases of l30l50 F. is attained, as measured by a spear thermometer inserted into the center of the case. No turning of the stems during sweating is required.

A reconstituted sheet substantially the same as made in Example 2 was obtained.

It is seen from examples that the sheet strength of formulations made with refined sweated stems is significantly higher than that of similar formulations made with refined unsweated stems.

EXAMPLE 6 Pennsylvania stems are softened, flattened, sweated, dried and threshed to produce it to A inch size pieces as in Example 2. Three hundred lbs. of these stems are charged into a suitable tank and 3,000 lbs. water added. The mixture is agitated for 10 minutes, then allowed to soak for 45 minutes. During this period the tobacco pieces rise to the surface. 1,000 lbs. of the water (containing tobacco solubles) is then drawn off from the bottom of the vessel through a drain valve which is equipped with a screen of such a design that it will retain tobacco stems but will allow small particles of sand or other foreign matter to escape with the efiluent. At the end of the draining period, sufficient fresh tap water is added to the batch to produce a stem-water mixture at 6 percent solids, and then refined to an inverted Schopper-Riegler freeness value of minus 200 cc., as in Example 2.

When the resultant partially washed refined sweated Pennsylvania stems were combined with Pennsylvania leaf in 70/30 proportions respectively and the resulting dispersion converted into reconstituted sheet as in Example 2, the resultant sheet at 5.0 grams/ft. sheet weight and at 26 percent moisture content had a breaking strength of l,050 grams/inch. This is substantially stronger than the counterpart formulation shown in Example 2 in which the sweated Pennsylvania stems were not washed prior to refining. In addition to the strength improvement, the sheet burn and taste properties were improved and a whiter and more coherent ash resulted.

EXAMPLE 7 The procedure of Example 6 was repeated exactly, except with the removal of all of the soak water (full wash) instead of only 1,000 lbs. of the soak water (partial wash procedure). The resulting reconstituted sheet (70/30 fully washed sweated Pennsylvania stems/Pennsylvania leaf dust) averaged 1,450 grams/inch breaking strength. As a result of this substantially increased strength, increased proportions of leaf dust may be incorporated into the formulation if desired.

EXAMPLE 8 Pennsylvania stems are softened, flattened, sweated, dried and threshed to produce M1 to 7% inch size pieces as in Example 2. However, instead of refining these stems at 6 percent solids and then subsequently combining the refined stems 70/30 with ground leaf dust as in Example 2, in this case the threshed to 1% inch stem pieces were blended 70/30 with Manila leaf portions (unground) and water added to produce an 8 percent solids mixture. This mixture is then refined and converted to reconstituted sheet as in Example 2. The resulting sheet had a sheet strength of 495 grams/inch at 24 percent moisture content. This is quite comparable to the 510 grams/inch at 23 percent moisture shown for the counterpart of this formulation in Example 2, where the stems were refined prior to the combination with a ground leaf dust compronent.

EXAMPLE 9 Sweated Pennsylvania stems are prepared and refined as in example 2. The refined Pennsylvania stems are then combined with Manila leaf dust in the ratio of 30 parts refined sweat Pennsylvania stems to 70 parts Manila leaf dust, on a solid basis with additional water to produce a solid content of 9.5 percent for the total dispersion. The dispersion was cast, dried and remoistened to about 24 percent moisture content as in the previous examples, except that the casting thickness was such that the resultant reconstituted tobacco sheet had a thickness of 9.3 grams/square foot. The sheet strength of this product, as measured on a 1-inch strip with a standard Scott Paper tester, was 360 grams/inc. The burn, taste, strength and thickness properties made it suitable for use as a cigar filler.

EXAMPLE l0 Sweated Pennsylvania stems were prepared and refined as in Example 2. The refined Pennsylvania stems were not combined with leaf dust in this case, but were cast directly on a moving stainless steel belt at the refining solids content of 6 percent. The dispersion was cast, dried and remoistened to about 24 percent moisture content as in the previous examples, with the casting thickness at a level to produce a reconstituted tobacco sheet at a thickness of only 3.0 grams/square foot. The sheet strength of this product, as measured on a 1- inch strip with a standard Scott Paper tester, was 720 grams/inch. Its taste, burn, strength and thickness rendered it particularly suitable as a cigar wrapper.

EXAMPLE 11 Sweated Pennsylvania stems are prepared and refined as in Example 2. The refined Sweated Pennsylvania stems are then combined with a tobacco dust component which is one-half Manila leaf dust and one-half Maryland stem dust. The overall ratio of components is 70/ l 5/ l 5 (refined sweated Pennsylvania stems/Manila leaf dust/Maryland stern dust), on a solids basis, with additional water added to produce a solid content of 8 percent for the total dispersion. The dispersion is converted into reconstituted tobacco sheet as per the previous examples at a thickness of 5.0 grams/square foot and 23 percent moisture content as in Example 2. The sheet strength, measured as in the previous examples was 545 gram/inch. The resultant product was particularly suitable for uses as cigar or cigarette filler.

It will now be seen that the previous invention provides for a simpler, easier, more economical procedure for the production of reconstituted tobacco products; a procedure which results in reconstituted tobacco product having characteristics far superior to those presently obtained.

What is claimed is:

l. The method of manufacturing a reconstituted tobacco product from stem particles, consisting essentially of the steps of mechanically working by crushing said stem particles so as to disrupt their cellular structure without substantially reducing the size thereof, refining said worked stem particles to a predetermined size, mixing said refined stem particles with an aqueous carrier to form a slurry thereof, shaping said slurry into a predetermined mass and drying said mass to a predetermined moisture level.

2. The method according to claim 1, wherein whole leaf particles are admixed with said refined stems.

3. The method according to claim 2 wherein said whole leaf is admixed with said refined stems in an amount between and 70 percent by weight of said stem particles.

4. The method according to claim 3 including crush flattening said stems to a size approximately 1-2 mils in thickness.

5. The method according to claim 3 including the step of refining said stem particles to a freeness value beyond the inversion point as measured on the Shopper Riegler Scale.

6. The method of manufacturing a reconstituted tobacco product from stem particles, consisting essentially of the steps of mechanically working by crushing said stem particles so as to disrupt their cellular structure without substantially reducing the size thereof, sweating said worked stem particles so as to expand their cellular structure, refining said worked and sweated stem particles to a predetermined size, mixing said refined stems with an aqueous carrier to form a slurry thereof, shaping said slurry into a predetermined mass and drying said mass to a predetermined moisture level.

7. The method according to claim 6 wherein whole leaf particles are admixed with said sweated stems in an amount between 0 and 70 percent by weight of said stems.

8. The method according to claim 7 wherein the stem particles are refined to a freeness value beyond the inversion point as measured on the Shopper-Riegler Scale. 7

9. The method of manufacturing a reconstituted tobacco product from stem particles consisting essentially of the steps of mechanically working by crushing said stern particles so as to disrupt their cellular structure without substantially reducing the size thereof, mixing said worked stem particles with an aqueous carrier, causing the soluble constituents of said stem particles to dissolve in said carrier, removing at least a portion of said carrier with said dissolved constituents, refining said soluble constituent-free stem particles to a predetermined size, mixing said refined stem particles with an aqueous carrier to form a slurry thereof, shaping said slurry into a predetermined mass and drying said mass to a predetermined moisture level.

10. The method according to claim 9 wherein said stem particles are soaked with said carrier for at least one-half hour under nation.

11. Tie method according to claim 10 wherein all of said carrier containing dissolved constituent is replaced.

12. The method according to claim 9 including the step of sweating said stems for a period in excess of one week prior to the removal of said soluble constituents.

13. The method according to claim 9 including the steps of mixing an amount of whole leaf not exceeding 70 percent by weight of stem particles with said stem particle prior to refinmg.

14. A reconstituted tobacco product made in accordance with claim 6.

15. A reconstituted tobacco product made in accordance with claim 9.

16. The method of manufacturing a reconstituted product from stem particles comprising the steps of mechanically working by crushing said stem particles so as to disrupt their cellular structure without substantially reducing the size thereof, sweating said worked stern particles at a temperature in a range between F. through F. for a period of at least 1 week so as to expand their cellular structure, admixing with said reconstituted stems, in an amount between 0 and 70 percent by weight, based on the weight of said stems, whole leaf particles, refining said worked and sweated stem particles containing said admixed whole leaf particles to a predetermined size, mixing said refined stems containing said admixed whole leaf particles with an aqueous carrier to form a slurry thereof, shaping said slurry into a predetermined mass and drying said mass to a predetermined moisture level.

17. The method, according to claim 9, wherein the soluble constituent-free stem particles are refined to a point at which the freeness of said slurry is beyond the inversion point on the Shopper-Riegler Scale.

18. The method according to claim 1 wherein the mechanically worked stems are washed with a dilute solution of a mineral acid. 

2. The method according to claim 1, wherein whole leaf particles are admixed with said refined stems.
 3. The method according to claim 2 wherein said whole leaf is admixed with said refined stems in an amount between 0 and 70 percent by weight of said stem particles.
 4. The method according to claim 3 including crush flattening said stems to a size approximately 1-2 mils in thickness.
 5. The method according to claim 3 including the step of refining said stem particles to a freeness value beyond the inversion point as measured on the Shopper Riegler Scale.
 6. The method of manufacturing a reconstituted tobacco product from stem particles, consisting essentially of the steps of mechanically working by crushing said stem particles so as to disrupt their cellular structure without substantially reducing the size thereof, sweating said worked stem particles so as to expand their cellular structure, refining said worked and sweated stem particles to a predetermined size, mixing said refined stems with an aqueous carrier to form a slurry thereof, shaping said slurry into a predetermined mass and drying said mass to a predetermined moisture level.
 7. The method according to claim 6 wherein whole leaf particles are admixed with said sweated stems in an amount between 0 and 70 percent by weight of said stems.
 8. The method according to claim 7 wherein the stem particles are refined to a freeness value beyond the inversion point as measured on the Shopper-Riegler Scale.
 9. The method of manufacturing a reconstituted tobacco product from stem particles consisting essentially of the steps of mechanically working by crushing said stem particles so as to disrupt their cellular structure without substantially reducing the size thereof, mixing said worked stem particles with an aqueous carrier, causing the soluble constituents of said stem particles to dissolve in said carrier, removing at least a portion of said carrier with said dissolved constituents, refining said soluble constituent-free stem particles to a predetermined size, mixing said refined stem particles with an aqueous carrier to form a slurry thereof, shaping said slurry into a predetermined mass and drying said mass to a predetermined moisture level.
 10. The method according to claim 9 wherein said stem particles are soaked with said carrier for at least one-half hour under agitation.
 11. The method according to claim 10 wherein all of said carrier containing dissolved constituent is replaced.
 12. The method according to claim 9 including the step of sweating said stems for a period in excess of one week prior to the removal of said soluble constituents.
 13. The method according to claim 9 including the steps of mixing an amount of whole leaf not exceeding 70 percent by weight of stem particles with said stem particle prior to refining.
 14. A reconstituted tobacco product made in accordance with claim
 6. 15. A reconstituted tobacco product made in accordance with claim
 9. 16. The method of manufacturing a reconstituted product from stem particles comprising the steps of mechanically working by crushing said stem particles so as to disrupt their cellular structure without substantially reducing the size thereof, sweating said worked stem particles at a temperature in a range between 130* F. through 150* F. for a period of at least 1 week so as to expand their cellular structure, admixing with said reconstituted stems, in an amount between 0 and 70 percent by weight, based on the weight of said stems, whole leaf particles, refining said worked and sweated stem particles containing said admixed whole leaf particles to a predetermined size, mixing said refined stems containing said admixed whole leaf particles with an aqueous carrier to form a slurry thereof, shaping said slurry into a predetermined mass and drying said mass to a predetermined moisture level.
 17. The method, according to claim 9, wherein the soluble constituent-free stem particles are refined to a point at which the freeness of said slurry is beyond the inversion point on the Shopper-Riegler Scale.
 18. The method according to claim 1 wherein the mechanically worked stems are washed with a dilute solution of a mineral acid. 